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<title>Kinktober 2020 - Day 28: Distension (Nightkiller, NSFW) by yastaghr</title>
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<h1><a href="https://archiveofourown.org/works/27249841">Kinktober 2020 - Day 28: Distension (Nightkiller, NSFW)</a> by <a class='authorlink' href='https://archiveofourown.org/users/yastaghr/pseuds/yastaghr'>yastaghr</a></h1>

<table class="full">

<tr><td><b>Series:</b></td><td>Yastaghr's Kinktober 2020 [28]</td></tr>

<tr><td><b>Category:</b></td><td>Undertale (Video Game)</td></tr>

<tr><td><b>Genre:</b></td><td>Alternate Universe - Dreamtale (Undertale), Alternate Universe - Killertale (Undertale), Animal Ears, Animal Play, Animal Transformation, Caring Dreamtale Nightmare Sans (Undertale), Distension, Dreamtale Nightmare Sans (Undertale), Dreamtale Nightmare Sans/Killer Sans (Undertale), Explicit Consent, Killer Sans (Undertale) - Freeform, Kinktober, Kinktober 2020, M/M, POV Dreamtale Nightmare Sans (Undertale), Size Kink, Tails</td></tr>

<tr><td><b>Language:</b></td><td>English</td></tr>

<tr><td><b>Status:</b></td><td>Completed</td></tr>

<tr><td><b>Published:</b></td><td>2020-10-28</td></tr>

<tr><td><b>Updated:</b></td><td>2020-10-28</td></tr>

<tr><td><b>Packaged:</b></td><td>2021-05-18 09:20:33</td></tr>

<tr><td><b>Rating:</b></td><td>Explicit</td></tr>

<tr><td><b>Warnings:</b></td><td>No Archive Warnings Apply</td></tr>

<tr><td><b>Chapters:</b></td><td>1</td></tr>

<tr><td><b>Words:</b></td><td>576</td></tr>

<tr><td><b>Publisher:</b></td><td>archiveofourown.org</td></tr>

<tr><td><b>Story URL:</b></td><td>https://archiveofourown.org/works/27249841</td></tr>

<tr><td><b>Author URL:</b></td><td>https://archiveofourown.org/users/yastaghr/pseuds/yastaghr</td></tr>

<tr><td><b>Summary:</b></td><td><div class="userstuff">
              <p>Nightmare discovered something about himself. Killer is quick to take advantage of it.</p>
            </div></td></tr>

<tr><td><b>Relationships:</b></td><td>Sans/Sans (Undertale)</td></tr>

<tr><td><b>Series:</b></td><td>Yastaghr's Kinktober 2020 [28]</td></tr>

<tr><td><b>Series URL:</b></td><td>https://archiveofourown.org/series/1947772</td></tr>

<tr><td><b>Comments:</b></td><td>8</td></tr>

<tr><td><b>Kudos:</b></td><td>91</td></tr>

</table>

<a name="section0001"><h2>Kinktober 2020 - Day 28: Distension (Nightkiller, NSFW)</h2></a>
<div class="story"><div class="userstuff module">
    
    <p>
  <span>“Are you still sure you want to try this, Killer? I do not mind leaving this particular bit of curiosity unsatisfied,” Nightmare asked for consent for this scene one last time. Despite what his brother sometimes thought he was all about consent. </span>
</p><p>
  <span>Killer laughed his delightfully unhinged laugh and it sent a thrill down Nightmare’s spine. He loved the way his datemate sounded when he was experiencing that particular emotion, even if it hurt him a bit when he felt it. He’d rather Killer be happy than not be in pain. Besides, Killer had helped him to see that pain wasn’t always a bad thing.</span>
</p><p>
  <span>“boss, you might not mind it, but i definitely do,” Nightmare would have protested that, but Killer interrupted him with more, better reasons for them to go through with this. “besides, you know i love being stretched by your tentacles, and we’ve been working towards this for weeks. i think i can handle it. so, please, crawl inside my pussy you sexy black octopus~ i wanna feel your whole body pushing my snatch to it’s limit.”</span>
</p><p>
  <span>Nightmare’s blush was instant and bright. Damn it, Killer knew how much his stupid little dirty talk got to Nightmare! He pushed Killer over onto his back and stole his mouth in a kiss, the liquid hate sizzling on his tongue. His hands and tentacles roamed over his lover’s naked body. </span>
</p><p>
  <span>“woah, nightmare, you getting a little </span>
  <em>
    <span>handsy</span>
  </em>
  <span> there?” Killer teased.</span>
</p><p>
  <span>Nightmare glared at him. “Shut up and form your pussy already! I can’t slip inside anything if it’s not there for me to work with!”</span>
</p><p>
  <span>Killer’s cheeky grin didn’t waver, but his cunt did snap into existence. It was bright red and marked with black splotches. They weren’t bruises; no, they were spots like you’d see on a leopard. Killer was such a show off. At least he hadn’t- oh, no. His matching leopard ears and tail had popped up on his skull and tailbone.</span>
</p><p>
  <span>Nightmare haughtily ignored them and started shifting his form. He wasn’t </span>
  <em>
    <span>exactly</span>
  </em>
  <span> switching into his shadow form, and he wasn’t </span>
  <em>
    <span>exactly</span>
  </em>
  <span> becoming goop. He was taking on a more solid and flexible form. It was that of an actual octopus. They’d discovered it a few weeks ago. Once he was in that form, Nightmare used it to do what octopi do best; slip through incredibly small openings like they were the widest of gateways. Then he looked around. </span>
</p><p>
  <span>He wasn’t sure what he’d expected Killer’s cunt to look like from the inside, but “see-through” hadn’t been it. If he avoided the black splotches he could actually see their bedroom! Interesting. His inner Sans was already planning pranks. Killer would be down for anything.</span>
</p><p>
  <span>He rotated inside the space, examining it from every angle and gently stroking it in the process. When Killer began to squeeze, Nightmare grinned. There he went. He then did something… mildly cruel. He expanded his octopus body as much as he could manage, distending Killer’s cunt just as his orgasm ripped through him. He could </span>
  <em>
    <span>feel</span>
  </em>
  <span> Killer’s scream, not just in his magic, but in his body! It felt exquisite!</span>
</p><p>
  <span>Only when Nightmare was sure that Killer’s orgasm had finished did he slide out of his lover. He landed on their bed with a splat. He didn’t have time to change back before Killer snatched him up in his arms and snuggled him. “fuck, boss~ we’ve </span>
  <em>
    <span>got</span>
  </em>
  <span> to do that again sometime. it was great!”</span>
</p>
  </div><div class="fff_chapter_notes fff_foot_notes"><b>Author's Note:</b><blockquote class="userstuff"><p>You can find me on:</p><p>Tumblr - https://yastaghr.tumblr.com<br/>Twitter - https://twitter.com/yastaghr * Most active</p></blockquote></div></div>
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